Exhaust gas turbocharger for an internal combustion engine

ABSTRACT

In an exhaust gas turbocharger for an internal combustion engine including an exhaust gas turbine and a compressor connected to the turbine so as to be operated thereby, the turbine includes a housing consisting of an inner and an outer shell formed from steel sheets and being arranged in spaced relationship so as to form therebetween an intermediate space.

BACKGROUND OF THE INVENTION

[0001] The invention relates to an exhaust gas turbocharger for aninternal combustion engine including an exhaust gas turbine and acompressor driven by the exhaust gas turbine, wherein the turbinecomprises a turbine housing with a turbine wheel rotatably supported inthe turbine housing.

[0002] DE 28 43 202 discloses an exhaust gas turbocharger which includesan exhaust gas turbine driven by the exhaust gases of an internalcombustion engine and a compressor, which is coupled to the turbine by ashaft for rotation with the turbine and which compresses inductedcombustion air to a charge pressure with which the combustion air issupplied to the cylinder inlets of the internal combustion engine. Thehousing of the exhaust gas turbocharger consists of three individualhousings for the turbine, for the compressor and for the bearing betweenthe turbine and the compressor. Each individual housing is formed as acasting wherein the housing for the turbine and the compressor, whichare arranged at opposite sides of the bearing housing, include also thesupply and the discharge passages for the turbine and, respectively, thecompressor.

[0003] The housings, which are manufactured by casting, can be producedinexpensively and they also provide for the necessary safety if theturbine or the compressor wheel should burst. They are however heavy,particularly for utility vehicle applications because they arerelatively large, and they require expensive and complicated connectingand support elements for their support in the vehicle. In addition,those high-mass housing have the disadvantage that, because of theirhigh heat capacity, a large amount of heat is stored in the walls of thehousings. As a result, a relatively large amount of heat is removed fromthe exhaust gas supplied to the turbine, whereby the energy supplied tothe turbine wheel is reduced which results in power losses particularlyafter a cold start of the engine.

[0004] On the other hand, there is the problem that, after shut down ofthe engine, the heat stored in the housing, particularly in the area ofthe turbocharger, may lead to coking of the oil in the charger. The hightemperatures may further result in thermal stresses in the housing. Inorder to avoid excessively high thermal stresses, the housings must beprovided with complicated cooling systems whereby the already largeweight is further increased.

[0005] Another disadvantage resides in the fact that, because of theremoval of heat from the exhaust gas, the catalytic converter isinsufficiently heated particularly at the beginning of the engineoperation so that the catalytic converter becomes fully effective onlywith a certain time delay.

[0006] It is the object of the present invention to provide a 25turbocharger, which is of a simple design but has a high efficiency. Itshould also have a relatively low weight.

SUMMARY OF THE INVENTION

[0007] In an exhaust gas turbocharger for an internal combustion engineincluding an exhaust gas turbine and a compressor connected to theturbine so as to be operated thereby, the turbine includes a housingconsisting of an inner and an outer shell formed from steel sheetsarranged in spaced relationship so as to form therebetween anintermediate.

[0008] A coolant may be conducted through the space between the sheetmetal shells. The two metal shells, which delimit particularly a spiralpassage for guiding the exhaust gas to the turbine wheel, are—comparedwith the cast components of the state of the art—relatively lightweightsince the relatively thin sheet metal walls are substantially lighterthan the cast walls. Inspite of the small wall thickness, they have ahigh burst resistance. Another advantage is the low heat storagecapacity of the double wall of sheet metal whereby the thermalefficiency of the turbocharger and also the start-up behavior of thecatalytic converter of the respective engine are improved. There is noneed for providing the heat shield panels by means of which theradiation heat has been contained in the past.

[0009] In a particular embodiment, the inner and outer sheet metalshells consist of sheet steel wherein the outer sheet consists oftemperature resistant material and the inner sheet consists of ahigh-temperature resistant material. The inner metal shell is in directcontact with the hot exhaust gas and is therefore heated to a greaterdegree than the outer metal shell, which is not contacted by the hotexhaust gas. The inner shell, which delimits the spiral inlet passageand which consists of a highly temperature resistant material isselected so that it is resistant to the high exhaust gas temperatures.The outer shell, which extends around the inner shell, however is not incontact with the exhaust gas so that it can be made of a material withlower temperature resistance than that of which the inner shell is made.

[0010] The inner shell as well as the outer shell can be shaped partsformed by suitable deformation techniques, such as internalhigh-pressure shaping procedures, from planar metal sheets. They mayhave complex shapes to form for example the spiral gas inlet channel ofthe turbine. It is also possible to form a spiral inlet with two inletpassages from a single inner shell, the two passages of the spiralchannel being separated by a divider wall, which is formed by anappropriate shaping of the inner shell.

[0011] The inner and the outer shells are preferably constructed so asto be separated from the exhaust channel of the turbine wherein theturbine wheel is supported. The exhaust channel which, at the oppositeside of the turbine wheel, may be connected with a bearing housing ispreferably a casting which is capable of withstanding the static anddynamic forces of the turbine wheel and which is capable of maintainingits original shape and dimensions. The inner and the outer shells areseparate from the outlet channel and are therefore not subjected to thehigh forces effective on the turbine wheel. The heat generated by theturbine wheel is generally taken up and conducted out by way by theexhaust channel so that the inner and outer shell remain to a largedegree unaffected by the heat generated by the turbine wheel.

[0012] The intermediate space between the inner and the outer shells mayaccommodate a coolant, which, in a preferred embodiment, is admitted byway of inlet nozzles and discharged by way of outlet nozzles. In anotherembodiment, the turbine housing, which consists of inner and outershells, may form a single component with an exhaust manifold, which ismounted to the cylinder outlet of the internal combustion engine.

[0013] The invention will become more readily apparent from thefollowing description of particular embodiments thereof on the basis ofthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a cross-sectional view of a turbine housing with atwo-channel spiral inlet structure,

[0015]FIG. 2 is a cross-sectional view of a turbine housing with asingle-channel spiral inlet structure,

[0016]FIG. 3 is a side view of the exhaust gas turbine housing accordingto FIG. 2,

[0017]FIG. 4 is a front view of the exhaust gas turbine housing of FIG.2, and

[0018]FIG. 5 is a top view of the exhaust gas turbine of FIG. 2 formedintegrally with an exhaust manifold of an engine.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0019] In the figures, identical parts are designated by the samereference numerals.

[0020] As shown in FIG. 1, the exhaust gas turbine of an exhaust gasturbocharger of an internal combustion engine which may be a gasolineengine or a Diesel engine and which may be installed in a passenger caror a utility vehicle, comprises a turbine housing 2 and a turbine wheel3 onto which the exhaust gas of the internal combustion engine isconducted so that the turbine wheel is rotated thereby. The turbinewheel 3 is rotatably supported in an exhaust channel 4 of the exhaustgas turbine and is connected to a shaft 5 for rotation therewith. Therotation of the turbine wheel 3 is transmitted, by way of the shaft 5,to the impeller of the compressor of the exhaust gas turbocharger forcompressing the intake air. The exhaust channel 4 is connected to abearing housing 6 by means of connecting elements 7. The exhaust channel4 and the bearing housing 6 are disposed at opposite sides of theturbine wheel 3. The turbine housing 2 is of a double-wall design andcomprises an inner shell 8 and a spaced outer shell 9, which togetherform a spiral turbine inlet channel 10. In the embodiment as shown inFIG. 1, the inlet channel 10 includes two inlet passages, that is, afirst inlet passage 10 a and a second inlet passage 10 b.Exhaust gasfrom the cylinder exhaust of the internal combustion engine is suppliedto the turbine wheel 3 by way of an inlet area 11 from the spiralchannel 10 and is then conducted, by way of the exhaust channel 4, to adownstream catalytic converter. The two inlet passages 10 a and 10 b areseparated from each other inside the spiral channel 10 by a divider wall12, which is formed integrally with the inner shell 8. The plane of thedivider wall 12 intersects the inlet area 11. In the example as shown inFIG. 1, the divider wall 12 however does not extend into the inlet area11. Rather, near the inlet area 11, the two flow passages 10 a and 10 bare joined to permit a gas exchange between the two flow passages.

[0021] The inner shell 8 and the outer shell 9 of the turbine housing 2are spaced from each other and form an intermediate space 13 throughwhich advantageously a coolant can be conducted. The coolant isintroduced by way of an inlet nozzle 14 and is discharged by way of anoutlet nozzle 15, which are both arranged in the outer shell 9. In theintermediate space 13, between the inner shell 8 and the outer shell 9,there are provided support ribs 16 by which the inner and outer shells 8and 9 are supported with respect to each other. The support ribs 16 actalso as reinforcement ribs to make the turbine housing 2 more rigid andto improve its overall strength.

[0022] The inner shell 8 and the outer shell 9 consist of sheet metal,especially of sheet steel and can be manufactured by a mechanicaldeforming process. The divider wall 12 separating the two inlet flowpassages 10 a and 10 b is formed integrally with the wall of the innershell 8, whereby the inner shell 8 has a closely heart-shapedcross-section. The outer shell 9 surrounds the inner shell withoutprojections or recesses in its contour. The inner shell 8 consistspreferably of a highly temperature resistant sheet steel; the outershell 9 is not exposed directly to the high exhaust gas temperatures andconsists therefore only of a temperature resistant sheet steel.

[0023] The inner shell 8 and the outer shell 9 are manufactured asindividual components separate from the exhaust channel 4 and thebearing housing 6. When assembled, the inner shell 8 and the outer shell9 radially surround the inlet area 11 between the exhaust gas outletchannel 4 and the bearing housing 6 by way of which the exhaust gasflows from the inlet flow passages 10 a and 10 b onto the blades 3 b ofthe turbine wheel 3. The connecting element 7 disposed in the inlet area11 between the exhaust channel 4 and the bearing housing 6 may be in theform of a flow guide structure by which a desired momentum is impartedto the exhaust gas which is directed onto the turbine wheel 3. Theconnecting element 7 may be part of a variable turbine inlet geometryfor the variable adjustment of the inlet flow cross-section to theturbine wheel 3.

[0024] The exhaust channel 4 and the bearing housing 6 are preferablycastings. The inner shell 8, which is disposed on the outside of theexhaust channel 4, and the bearing housing 6 are preferably gas- andpressure-tight in order to avoid flow and pressure losses.

[0025] In the embodiment of FIG. 2, the exhaust gas turbine 1 includes aspiral inlet channel 10 with a single inlet flow passage, which is incommunication, by way of the inlet area 11, with the exhaust channel 4and the turbine wheel disposed therein. The connecting element 7 ispreferably in the form of a stationary guide structure. In addition, avariable turbine geometry 17 may be disposed in the turbine inlet area11 for example in the form of a guide vane structure with variablevanes, which can be moved by a control element 18 between a closedposition in, which the flow cross-section of the inlet area isminimized, and an open position, in which the exhaust gas flow throughthe turbine in unrestricted.

[0026] From the representations of FIGS. 3 and 4, it is apparent thatthe turbine housing is connected to an exhaust gas manifold 19 whereinan expansion-accommodating element 20 (FIG. 3) may be provided for theinterconnection. The turbine housing 2 is connected to the exhaustchannel 4 and the bearing housing by struts 21 and 22.

[0027]FIG. 5 shows an arrangement wherein the turbine housing is formedintegrally with the exhaust manifold.

What is claimed is:
 1. An exhaust gas turbocharger for an internalcombustion engine comprising: an exhaust gas turbine and a compressorconnected to said exhaust gas turbine so as to be driven by the turbine,said exhaust gas turbine including a turbine housing, said turbinehousing consisting of two spaced structures of sheet metal, one formingan inner shell and the other forming and outer shell surrounding saidinner shell in spaced relationship so as to form an intermediate spacebetween said inner and outer shells.
 2. An exhaust gas turbine accordingto claim 1, wherein said inner and said outer shells are formed fromsteel sheets.
 3. An exhaust gas turbine according to claim 2, whereinsaid outer shell is formed from a temperature-resistant steel.
 4. Anexhaust gas turbine according to claim 3, wherein said inner shell isformed from high-temperature resistant sheet steel, which has a highertemperature resistance than the sheet steel from which said outer shellis formed.
 5. An exhaust gas turbine according to claim 1, wherein saidinner shell and said outer shell are shape-pressed from metal sheets. 6.An exhaust gas turbine according to claim 1, wherein said inner shelldefines a turbine inlet with two inlet flow passages, which are formedby an inwardly extending divider wall portion of said inner shell fordividing the spiral inlet channel of said turbine into said two flowpassages.
 7. An exhaust gas turbine according to claim 1, wherein saidinner shell forms a single spiral inlet flow passage for directingexhaust gas to said turbine wheel.
 8. An exhaust gas turbine accordingto claim 1, wherein said outer shell includes an inlet nozzle forsupplying a coolant to the intermediate space between said inner andouter shells and an outlet nozzle for discharging the coolant from saidintermediate space.
 9. An exhaust gas turbine according to claim 1,wherein said turbine includes an exhaust channel and said turbine wheelis disposed in said exhaust channel, said exhaust channel, said innershell and said outer shell being separate components.
 10. An exhaust gasturbine according to claim 9, wherein said exhaust channel is a casting.11. An exhaust gas turbine according to claim 1, wherein said innershell and said outer shell form a turbine housing which forms anintegral component with the exhaust manifold connected to cylinderexhaust gas outlets of an internal combustion engine.
 12. An exhaust gasturbine according to claim 1, wherein support ribs are provided in theintermediate space between said inner and said outer shells forsupporting said inner and said outer shells relative to each other.